1. Field of the Invention
The present invention relates to a receiver for receiving marine-related information transmitted by a radio communications system, such as NAVTEX (which stands for Navigational Telex).
2. Description of the Related Art
Today, the Global Marine Distress and Safety System (GMDSS) plays an important role as a communications system used in relation to distress and safety at sea. The GMDSS makes use of satellite communications and digital communications technologies to enable sea-going ships in any areas to quickly obtain maritime safety information and meteorological information provided from coastal stations by automatic reception. For example, when a ship is in distress at sea, the GMDSS can be used to request search and rescue organizations and nearby ships to promptly initiate search and rescue operation in a reliable fashion regardless of in which area the ship in distress is currently located. Designated as a vital element of the GMDSS, NAVTEX is a radio communications system for the broadcast and automatic reception of marine-related information provided chiefly to ships navigating within approximately 300 nautical miles from the coast. NAVTEX services include transmission of maritime safety information, such as navigational warnings and meteorological warnings and forecasts, in the from of English or Japanese text data, for example, as well as automatic reception of each message, which will be printed or displayed on-screen by NAVTEX receivers installed on-board ships in a service area. Conventionally, most NAVTEX receivers are designed to sequentially print out messages which have been obtained by receiving and demodulating NAVTEX signals on a strip of paper. Since the NAVTEX signals only include information on navigational, meteorological, distress and other safety-related events within a service area and on latitude and longitude at which each event has taken place in the from of text data, however, it is not so easy to acquire and utilize such information that is needed for navigational purposes by own ship.
Japanese Patent Application Publication No. 1999-271087 discloses a shipborne navigational display system for acquiring and displaying information necessary for navigational purposes of own ship. Incorporating a built-in chart display feature, this system acquires information on an event and latitude/longitude at which the event has taken place from various pieces of information obtained from the GMDSS and displays the site of the event on an on-screen electronic chart.
The conventional NAVTEX receivers sequentially print out individual events together with latitude/longitude information contained in received messages on a strip of paper, for example, as stated above. Thus, if a user wishes to know the distance from own ship to the site of a particular event from the printed information, the user is forced to undertake demanding work of manually calculating the distance from information on latitude/longitude of the receiver and the latitude/longitude information for that event.
While the aforementioned shipborne navigational display system of Japanese Patent Application Publication No. 1999-271087 is advantageous in that individual events are intuitively presented on the electronic chart display based on the latitude/longitude information for the events, the system does not enable the user to directly recognize the distance from own ship to the site of each event. In addition, as this shipborne navigational display system is an integrated system incorporating not only a NAVTEX receiver but other apparatuses, such as a chart display device, the system is large in size and requires complicated operation and control.